Multiple Sclerosis (MS), an autoimmune disease of the central nervous system, is the leading cause of non- traumatic neurological disability among young adults. Although MS is classically associated with motor impairment, individuals with MS typically experience a constellation of symptoms including pain, fatigue, cognitive dysfunction, and depression. These symptoms can exacerbate or produce functional limitations that are in excess of those that are attributable to MS-related neurological damage. The progressive nature of MS results in a typical course of increasing symptoms and disability over a lifetime. Consequently, identifying ways to manage symptoms and achieve and maintain optimal functioning is a primary goal for MS clinical researchers. Unfortunately, the nature of symptoms, including the co-occurrence and variability in common symptoms, and the role of symptoms in functioning in MS, is not well characterized. To address the gaps in the current research resulting from reliance on retrospective self-report of global symptoms and an overly-narrow focus on one or a few symptoms at a time, this study will assess multiple symptoms and functional outcomes over the course of seven days in a sample of adults with MS. Use of ecological momentary assessment and accelerometer technology will provide repeated, real-time assessment of symptoms and functioning across the day. These highly reliable and ecologically-valid means of collecting data will provide a unique and multifaceted view of the lives of those living with MS. Over the course of the week-long data collection period, objective measures of participant physical functioning will be assessed via a wrist-worn accelerometer (a device that detects and records body movement) and subjective measures of daily functioning will be assessed by means of self-reported participation in 28 physical and non-physical activities (e.g. self-grooming, staying connected with friends). To measure symptoms, participants will be prompted to enter ratings of pain, fatigue, cognitive functioning, and depression into the accelerometer device at five times throughout the day. A more lengthy assessment of average daily symptoms will be completed each night. These data will be used to describe the fluctuations of and associations between MS symptoms. Examination of temporal associations between symptoms may reveal whether some symptoms precipitate or exacerbate other symptoms (e.g. pain flares resulting in cognitive problems). This study will also explore the association between symptoms and functioning, with a focus on whether there are specific associations between particular symptoms and functional domains (e.g. fatigue with physical activity, depression with social activity). The findings from this study could lead to better understanding of how symptoms affect functioning in the daily lives of those with MS, and can help to identify, develop, refine and tailor interventions. Clinicians may use this information to target the most impactful symptoms, or time medication administration or self-management strategies according to an individual patient's needs.